In U.S. Pat. No. 4,360,728, Drexler discloses a data card writing and reading system in which a laser light source emits a beam directed onto a flatly held card. In a coarse mode of operation a first servo-controlled mirror is mounted for rotation in order to find the lateral edges of a strip of laser recording material which is disposed on a surface of the card. Then, in a fine mode of operation data paths are identified which exist at predetermined distances from the edges. A second servo-controlled mirror is mounted for rotation in order to scan the beam in a fine mode of operation along the length of the card. Coarse control of the lengthwise position of the card is achieved by motion of a card shuttle.
When recording, the beam produces light scattering or absorbing spots in the laser recording material. The spots which represent data bits are aligned in parallel data tracks. The data bits are read by using a reduced power laser beam and a photodetector which detects differences in reflectivity between a spot and the surrounding material.
In U.S. Pat. No. 3,654,624, Becker et al. disclose a laser recording system in which a flat elongated record strip is wound around the surface of a drum. The drum is rotated with respect to the laser beam during recording and reproducing operations. By means of a servo-controlled linear positioning mechanism, the laser beam is moved transversely to the direction of drum rotation to permit selection of any one of a large number of spaced parallel scan lines on the record strip.
In U.S. Pat. No. 3,795,902 an optical reader is disclosed for reading digital data recorded in arcuate and spiral data tracks on a flat data record. A light beam is caused to scan across the data record along the curved data tracks. This provides high reading speeds, but many industries have adopted optical formats having straight, parallel data tracks.
Within the field of data cards there are occasions when there is a need to record several to perhaps thousands of data cards with the same or similar information. A typical optical card reader/writer has a recording speed of about 10,000 up to 100,000 data spots per second. Thus, it would require up to about 30 minutes to fill a single card with 2 megabytes of data. Although lasers are capable of generating pulses at a rate exceeding 200,000 per second the overall recording speed is reduced by the continuous accelerations and decelerations involved in card motion relative to a fixed laser, or vice versa. A need to synchronize laser beam pulses with the speed and position of the card also reduces the recording speed.
In U.S. Pat. No. 4,820,913 a data card recording system is disclosed which records identical data on each of a plurality of optical data cards supported around the surface of a drum. Each card contains a strip of optical recording material on its surface. The drum is mounted for rotation and may have flanges set in the circumference for gripping the longitudinal ends of the cards. Alternatively, the drum may comprise a pair of concentric cylinders in which the cards are mounted between the cylinders. The recording strips of these cards face outward. A light source emits a light beam which is directed along an optical path to the cards, so that as the drum rotates, the light beam produces data spots corresponding to a stored data segment.
The data tracks on the recording strips are aligned in the direction of drum rotation. The relative transverse position between the light beam and the cards is movable, as by moving an element in the beam path, so that additional data segments may be recorded in multiple parallel tracks on each of the cards. Recording is complete when the data cards are each filled with identical information or when all data segments have been recorded. A photodetector may be positioned for reading a track on a card, by measuring changes in the optical contrast of data spots and the surrounding recording material.
Although the above multi-card recording system duplicates cards very rapidly, the cards produced are not suited to all applications, particularly high speed reading with CCD arrays. Thus, in U.S. Pat. No. 4,912,312, a multiple-card recording system is disclosed in which the data cards are mounted to a rotatable drum with the length of the recording strips parallel to the axis of the drum. In contrast, then, to the prior drum recording system, wherein the recording medium had its lengthwise direction parallel to the direction of drum rotation, the recording system disclosed here has its widthwise direction parallel to the direction of drum rotation. As the drum rotates, each card passes a laser writer which records the same or a different data segment onto each card until the drum makes one complete revolution. Then, the laser writer is translated with respect to the cards and the next data segment or segments is written on each card. After completion of the next drum rotation the process is repeated and so on, until all the cards are completely written.
An advantage of this multi-card recording system is that by recording the data in a widthwise direction high speed card readers employing CCD arrays may be used. Such high speed readers read across the width of the card as the card is advanced through the reader. This allows the card to pass beneath the CCD array disposed over the data strip and provides for high speed reading of entire rows of data.
While the above two multi-card recording systems rapidly produce recorded data cards, these systems do not in themselves provide high speed reading of a particular data card. Moreover, while it is advantageous to record multiple cards with the same or similar data, at the same time, it is not generally required to read multiple cards at the same time. For this reason readers and writers for individual cards, like that disclosed in previously discussed U.S. Pat. No. 4,360,728, have been designed. With reader/writers designed for individual card use it is often desirable to have a compact design. And since these devices may also serve as remote facilities, such as automatic teller machines, it is desirable that they be highly reliable and require little maintenance.
Thus, in view of the above, it is an object of the present invention to design a high speed optical data card reader/writer for use with individual cards having straight, parallel data tracks.
It is another object of the present invention to design an optical data card reader/writer which is compact in design and which is highly reliable.